To improve fuel economy of automotive engines it is desirable to run the radiator fan only when ambient conditions are inadequate to dissipate enough heat. When the radiator (or engine) temperature reaches a given valve, a temperature responsive switch closes to energize the fan motor until the temperature falls to an acceptable level. Due to various design constraints, the thermostatic switch has been inadequate to handle the electrical load of the fan motor and this has meant that a relay operated switch was required. Thus, the thermostatic switch energized the relay which then closed the motor circuit.